A malformation of the nervous system caused by failure of the anterior neuropore to close. Infants are born with intact spinal cords, cerebellums, and brainstems, but lack formation of neural structures above this level. The skull is only partially formed but the eyes are usually normal. This condition may be associated with folate deficiency. Affected infants are only capable of primitive (brain stem) reflexes and usually do not survive for more than two weeks. (from menkes, textbook of child neurology, 5th ed, p247)

A rare neural tube defect during pregnancy, resulting in the absence of a large portion of the brain and skull in the fetus.

Congenital malformation of the nervous system caused by failure of the anterior neuropore to close; infants are born with intact spinal cords, cerebellums, and brainstems, but lack formation of neural structures above this level; the skull is only partially formed but the eyes are usually normal; affected infants are only capable of primitive reflexes and usually do not survive for more than two weeks; complete absence of the brain is rare.